Rotator for rock-drills.



c. T. GARNAHAN.

ROTATOR FOR ROCK DRILLS.

C. T. CARNAHAN.

ROTATOR FOR ROCK DRILLS.

APPLIGATION FILED 11111.22, 1911.

1,050,806. Patented .131121, 1913.

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UNTTED STATES PATENTY oEEIcE.

CHARLES T. CAENAHAN, oF DENVEE, coLonADo.

ROTATOB 'FOR lBCCIK-IIRIILS.

Speeication of Letters Patent.

Patented Jan. 21,1913;

Appncation'meafspru 22,1911. serial no. 622,848.

accompanying drawings, and to the chalaeters of reference lmarked thereon, which form a part of this specification.

My invention relates to improvements in rock drilling machines of the valveless hammer type. f

In the rotating lmechanism I employ two ratchet collars, the teeth of which engage each other. One of these collars carries antifrictional balls, which engage longitudinally disposed grooves formed in the adjacent portion of the casing, the said grooves being parallel with the axis of the machine.

2.5 The other collar carries similar balls which ehgage spirally arranged grooves formed in the tappet which `carries the drill steel or tool. The Vtoothedportions of the two eol' lars intermesh with -each other in such a 3Q manner that as the piston composed of these two collars moves lforwardlyunder the mf.

uenceof the motive fluid pressure l'in the-- Alow pressure chamber, the forward collar is caused` to move on its,companion-"cellarhyV virtue of the spiral grooves 'in the `tappeti;

while during .the return movement" of the said piston the forward collar is'ilocked against rotation in '1 the 4direction Vof the stress due tothe spiral-grooves in the tapAv 59 pet, and consequently the tappet must-. ro-

tate. 'In this manner the partial rotary movement is imparted to the, drill steel between vstrokes which is necessary in order to` change Ythe position of the cutting face of .45 the-tool after eachstroke. A novel feature of this rotating mechanisnris-A believed to be the employment f the antifrictional balls engaging the straight and spiral lgroovesI as aforesaid,; whereby the collars.- may be' subjected to considerable lateral strain, withoutmaterially interfering with.`

ltheir'movement in a longitudinal direction.

Having briefly outlined my improved construction, I will. -proceed to describe the 56 same in det-ail, reference being" made to the trated an .embodiment thereof.

In this drawing: Figure l is a central longitudinal section taken through a machine equlpped with my improved construction, the drill steel being omitted from the forward 'extremity of the machine and thevfeed bar casing being broken away in the rear. Fig. 2 is a similar view with the throttle valve portion of the machine broken away in the rear, and illustrating the drill bit or tool inserted in the tappet at the forward I i accompanyingdrawing in which is .illusl extremity of the machine, the hammerV being shown in its strikin position or in engage# ment with ,the drilL steel tappet. Fig.3 is a similar view, buft showing the hammer after it has commenced its rearward stroke and uncovered the exhaust ports leadingfrom the low pressure chamber, and before the piston composed of the ratchet collars has commenced its rearward stroke under the influence of its actuating spring. Fig. l 4 is a detail view in elevation of the tappet. Fig. 5 is an end elevation of the tappet looking in the direction of arrow 5, Fig. 4. Fig. 6 is a fragmentary view of the portion of the machine carrying lthe throttle valve, being substantiallyl the construction shown in` Fig. 1, `but. on a larger scale. Fig. 7 is a section taken on the line 7--7-, Fig. 6, viewed?. in the direction of the arrow. .F-ig. 8 is a section taken through the machine cutting the thrQttlevalveon/the line 8 9, Fig. 13.

9 is a similar view, showing the lvalve,

however, in a slightly changed position, the same having been given approximately-a quarter rot-ation from thev position shown in Fig.,8. Fig. 10 is a fragmentary section taken through -the machine cutting the throttle valveY on the line 10--11, Fig. 14.- In this view the valve is givenf apprpximately a quarter turn from the 1- position shown'in Fig. 9, whereby themotive tl'uid Dis turned on full tothe-engine, while it is also passing to the feed bar casing and uniting with the water for passage to the drillhole. Fig. 11 is asimilar view, but showing the valve in a different position, the mot-ive fluid, however, being still, turnedyon fullto the engine, but cut olf from the .iced bar casing. l Fig. 12is a top plan view A of the va1v a', o'r a viewlookingin the direc- ,tion of arrow 1 2-, F.ig. ;13. Fig. 13 is a side. elevation of the valve looking in the directionof arrow 13, Fig. 12. Fig. 121; is an ele-v o"forwardsmogement vation of the valve looking at right angles to Fig. 13 orin the direct1on of arrow 14, Fig. 12. j

The same reference characters indicate 5 the same parts in all the views.

Let the numeral 5 designate the drill cylinder provided with a chamber 6 in which is loca-ted a reciprocable hammer 7, which when at its rearward limit of movement has 1'0 its rear extremity in close ,proximity to a block 8 in which is located a throttle valve 9 for regulating the passage of motive fluid to the hammer chamber through a longitudinal passage v10 formed in the head block and lateral (passages 12 communicating with the longitu nal passagesat their inner extremities, and at thelr outer extremities with a circumferential groove 13 -in the head block, which communicates with a passage 14 formed in the wall of the cylinder and extending forwardly and communicating by a short lateral passage 15, with a circumferential groove 16 formed in the wall of the cylinder, and in communication with laterally extending passages 17 formed in the hammer and communicating with the central chamber 18 of the hammer. In this manner the motive fluid acts upon the hammer to drive the latter forward, and when at its extreme forward limit of movement it strikes the tappet or striking bar 19 which carries the drill steel20 (see Fig. 2). Just before the hammer reaches its forward limit of movement, its chamber 18 is placed in communication with a 'short passage 21 leadmg to'an expansion or low ressure chamber 22, whereby the motive uid acts'by .expansion to move vforward a piston 23 composed of two ratchet collars 24 and .25 hav 4f, `ing intel-meshing ratchet' teeth26, the forward collarY 25 being actedon byra spiral spring 27 which is placed under tension for imparting the reverse movement "to the ratchet plston. The rear collar 24 carries 4'5v steel balls 28 arranged to move in straight make a partial rotation in one`direction,

since its balls 30 travel in the spiral grooves 31 of the striking'bar. Hence the teeth of. the collar 25 must slip past the adjacent teeth of the collar 24. However, as, the

hammer recedes or makes the' return stroke,

andthe air exhausts from the expansion chamber forward of the piston 23, the recoil of the spring 27 acting on the said piston moves the same rearwardly.

` During this action the collar cannot rotate andthe collar 25 cannot rotate in the direction of stress, but as the balls 30 engage the spiral grooves of the striking ball, a partial rotation must be imparted to the latter, whereby a corresponding movement is imparted to the drill steel, as is required for effective work in a machine of this kind. As soon as the piston 23 is at its forward limit of movement, the hammer begins its rearward travel under the influence of motive fluid from the circumferential groove 16, which is in communication with the live motive fluid as heretofore explained, the hammer during its forward travel having brought its shoulder` 32 into communication with the said groove. The live motive fluid actingI upon the shoulder 32 drivesthehammer rearwardly more rapidly than the spring 27 imparts a similar travel to the piston 23, thus 'prolonging exposure of lexhaust ports 33 through which lthe motive fluid in the low pressure chamber exhausts to the atmosphere. The exhaust through the ports 33, however, is supplemented by a further exhaust through grooves 34 formed in the striking bar, (see Fig. 5), the said grooves being in communication with the chamber 35 in which the spring 27 is located, the said chamber being in communication with a port 36 leading to the atmosphere.

The construction of the throttle valve 9, andthe manner in which it serves to control the passage of motive fluid to the llammer cylinder and the feed bar casing, will now be described, as will also the manner of controlling the passage of water and air to the hollow drill steel for the purpose of removing the rock cuttings from the drill hole. y

The throttlevalve 9 is frusto-conical in shape and occupies a counterpart opening 37' formed in thgwhilLllLQCliiY. 'lfllclower portion of this valve has a central vertical opening 38 communicating` at its upper eX- tremity with lateral passages-39 extending in opposite directions through the valve, and at its lower 'extremity with a passage 40 formed in an elbow 41 adapted to be connected 'with a source of motive fluid for operating the drill. This elbow is screwed into a socket formed directly beneath the valve opening 37 of the head block, there being a space 42 between the elbow and the valve whereby the valve is subjected to upward pressure and as its low'er extremity is largest, this action of the -motive fluid keeps the valve tight in the head block at all times regardless of wear. When the valve is turned in such position that one ofl its openings 39 is in communication with the passage 10 of the head block, the" motive fluid is turned into the hammer cylinder to the maximum capacity. The throttle valve is further provided with two passages 43 and 44 in communication with an opening 45 formed in the valve above the openings 39, the said openings 43 and 44 communicating at their outer extremities with grooves 46 and 47 which eX- tend in a circumferential direction around the valve, diminishing in size from the openings 43 and 44. One of these openings means of a passage 52 (see Figs. 6 and 7) with a'passage 53 formed in an elbow 5 connected with a suitable source of water supply, not shown. Hence by virtue of the construction just described, when the valve is properly adjusted (see Figs. 10 and 11), air will enter the angular passage 48 of the head block from a passage 43 or 44, simultaneously with the entrance of water to the angular passage through the passage 50 of the head block which is in communication with the groove 51 and elbow passage 53 for supplying water as aforesaid. The air and waterare carried through the angular passage to the circumferential groove 49,

thence through a relatively long passage 55 formed in the Wall of the drill cylinder, thence through a port 56 to a circumferential chamber 57 which is in communication with a port 58, the latter being in communication 'with a central passage 59 formed in the drill 20, whereby the water and air pass through the drill steel and may be constantly supplied to the drill hole for renoving the rock cuttings and alla-ying the ust. f

In order to form a Huid-tight joint, the striking bar 19 is surrounded on opposite sides of the chamber 57 withpackings 65 and 66 formed preferably of leather; By virtue of the forward packing 66 the escape of the air and water through the port 57 may be cut off lin case the drill should be started without the drill steel in place, since'in this event the striking bar would be moved forwardly a sufficient distance to cause the packing 66 to cover the outer extremity of the port 58, thus forming an air cushion in the chamber 57 and preventing the collar 67 formed on the striking bar, fromfmoving forwardly and injuring the machine by crushing the packing leathers and 66 together.

Between a screw plug 68 inserted in the forward extremity of the cylinder and through which the striking bar passes, and a Collar 69 located immediately forward of the packing washer 66, is located a packing 70 whose special function is to produce sumcient friction upon the striking bar to prevent the rotary action of the latter during the forward movement of the piston 23, or when the collar 25 moves on the collar 24, the teeth of the one collar slipping past those of the other collar. If the rotary action of the striking bar were not retarded by friction resulting from the use ofthe packing 70 or its equivalent, or in other words, if the striking bar rotated easily within the cylinder, it would rotate instead of the collar 25. By virtue of my improved construction, however,` the friction of the packing 7 0 makes it more diiiicult to rotate the striking bar than for the teeth of the collar 25 to slip past t-he teeth of its companion collar 24. Hence the construction operates-as it should; while if it were otherwise and the striking bar rotated* instead of the collar 25, the said bar would make a partial rotary movement during the forward movement of the piston 23, and reverse its action during the rearward -movement of the said piston, and consequently the face `of the drill steel would not change its position. In other words, the rotating mechanism would be inoperative. `At the same time the motive fluid may be supplied to the feed bar casing 61 through a passage 62 formed in the head block and in communication with the passage 44 of the throttle valve. When, however, it is not desired to supply motive fluid to the feed bar casing by reason of the fact that the material is so soft through which the drill steel is passing that. it is not desirable to use motive fluid to hold the drill in position, the valve may be turned to the position shown in Fig. 11, whereby thfmotive fluid is cut olf-from the passage 62, and the air is fed to the angular passage 48 of the head block, through the passage 44 of the valve, while the passage 43 is out of commission.

From the foregoing it will be understood that when the drill is regularly on operation, the throttle valve is in the position shown in Fig. 10; while when it is desired to run the drill in the regular way except that the motive Huid is cut off from the feed bar casing, the valve is given a half turn from the position shown in Fig. 10 or to the position shown in Fig. 11. In this event the passage 39 of `the valve through which the motive fluid passes to the central passage 10 of the head block when the valve is in the positionshown in Fig. 10, is thrown out of co'mmission, while the op osite passage39 bccomes that throughjw ich the motive yfluid enters the its way to t e hammer cylinder. When it is desired to exhaust the'motive iuid from the feed bar casing, the valve 9 is turned to the position shown in Fig. 8, whereby a lateral assage 10 of the head block on passage 63 formed in the valve is placed in communication with the passage 62 of the head block yleading to the feed bar casing. This lateral .passage 63 also communicates with a vertical passage 64' formed in the valve and through which the motive fluidV escapes to the atmosphere.

' From the foregoing description the use and operation of my improved rock drilling machine will be readily understood, and its various steps will now be briefly set forth in their proper sequence. If we assume that the throttle valve is in the position shown in Fig. 8, the feed bar casing is open to the atmosphere through the passage 62 of the head block and the passages 63 and 64 of the valve. At the same time the valve is in p0- sition to cut off the live motive Huid from the feed barI casing and the drill cylinder, and also to cut olf the water and air from the hollow drill steel andthe various passages forming the path for the water and air between the drill steel and the valve. Now if it is desired to start the machine, the valve may be given Aa, quarter turn (see Fig. 9), whereby a small amount of motlve fluid will be turned into the feed bar casing from the passage 44 of the valve, since the tapering groove 47 of the latter is slightl in communication with the passage 62 0 the head block leading to the feed bar casing. This will be Vsuflicient to set the drill against the rock. It will be noted that when the valve is in the position shown in Fig. 9, no motive fluid is turned into the cylinder, since neither passage 39 of the valve is in communication even to the smallest extent,

' with the passage 10 of the head block. The water and air, however, are delivered to the' angular passage 48, by virtue of the fact that one extremity of the groove 51 of the valve is in communication with the passage 50 of the head block leading to the angular passage 48, while the passage 43 0f the valve 1s also in communication-with the angular passage 48. Hence when the valve is in the position shown in Fig. 9, there is sufficient motive fluid turned into the feed bar casing to move the drill against the rock or into operative position, while a mixture of water and air is started on its way to the hollow drill steel. The valve will now be farther turned in the same direction, being that indicated by the arrow in Figs. 9 and 10, to the position shown in Fig. 410. Durin this operation the motive fluid is gradua ly turned into the hammer cylinder and into the feed bar casing until the maximum limit is reached, by virtue of the tapering grooves 46 and 47 which are respectivel in communication with the passages 43 andY 44, as heretofore explained. "Hence when the valve is in the position shown in Fig. 10, the machine is running in the regular way, the motive fluid being turned von to its full capacity, and a corresponding supply furnished to the feed bar'casing, whereby the drill is held up to its work in the proper manner. If now during the drillin operation a soft place in the rock shoul be encountered, as a streak of clay or material so soft that the pressure of the motive iuid in the feed bar casing would not be required, the operator may quickl turn the valve 'from the position shown 1n Fig. 10 to that shown in Fig. 1'1, the valve being given a half rotation so that the passage 39 on one side of the center of the valve which was out of commission when the valve was in the posltion shown in Fig. 10, will be in register with the passage 10 of the head block,

while the assage 39 which was formerly in register w1th the'said passage of the head block'is out of commission. At the same time communication of the live motive fluid with the feed bar casing is completely cnt olf, since'the passage 44 is thrown out of communication with the passage 62, while the passage 43 has not moved quite far enough to communicate with the passage 62 of the head block leading to the feed bar casing. The passage 44, nevertheless, supplies suicient motlve Huid to mingle with the water entering through the circular passage 51, so that the supply of the air and water mixture to the hollowdrill steel, as well as the complete supply of motive fluid to the'hammer'cylinder, 1s maintained. The valve will be kept in the position shown in Fig. 4 until the drill steel has passed through the soft spot in the rock and encountered material of the proper hardness to justify the use of the pressure supply from the feed bar casing to hold the machine up to its work. The motive fluid being turned into the hammer cylinder, imparts the necessary reciprocating movement to the hammer, the

motive fluid entering the central chamber of the hammer throu h the ports and passages as heretofore-expiined. During the time the hammer moves forward to its limit of movement, the motive fluid from the central chamber 18 of the hammer exhausts into the low pressure chamber 22 of the cylinder and acts upon the piston 23 composed of the two ratchet collars 24 and 25 and causes them to move forwardly, whereby the collar 25 is given a partial rotary movement on its companion collar 24 by virtue of the fact that the balls carried by the collar 25 engage thel spiral grooves of the striking bar, whereby the spiral spring 27 is compressed. Now as the hammerreoedes, due to the action of the motive fluid upon its exterior shoulder 32, the exhaust ports 33 are uncovered-and the exhaust from the chamber 18 of the hammer is completed through the said ports together with the grooves 34 of the striking bar, the spring chamber 35 and the port 36 leading from sald chamber tothe atmosphere. Simultaneously with the es' cape of the exhaust from the chamber 18 of the hammer into the low-pressure chamber 22, the forward extremity of the hammer enters the opening in the member 24 of the piston 23. As the hammer-extremity fitsY closely within the said piston-member 24,

the' exhaust which enters the low-pressure chamber from the chamber 18 of the hamJ mer, acts upon the piston 23 to move the latter forwardly, the hammer-ext-remity cutting off the escape of the exhaust from .the low-pressure chamber until the piston 23 has been actuated as aforesaid. It must be understood that the small exhaust ports 33 are not uncovered until the piston 23 is at its forward limit of movement, conse-1 quently there is no avenue of escape for thelexhaust from the chamber 18 after enteringA the low-pressure chamber, until the pistonlv 23 is atits forward limit of movement. The

exhaust then commences to a limited extent through the ports 33, but as soon as they hammer retreats suiiiciently to disengage it-l self from the menber 24 of the piston 23,

there is free exhaust through the opening in the piston 23 by way of the and the port36. It will thus be seen that the entrance of the forward extremity of the hammer into the opening of the ringmember 24 of the piston 23 is of the utmost importance in order to prevent the escape of the exhaust-motive-iuid from the lowpressure chamber 22 until the piston 23 has,

been actuated as aforesaid. The special construction of the piston 23 'is important. It-

must be'ringsshaped in order to allow the piston-hammer to enter it in order to strike the drill-steel holder.

Having thus described my invention, what I claim is: y A

1. A rock drilling engine, equipped with a rotatable vdrill steel, the said enginebeing provided with highl andlow pressure chambers, pistons in the respective cham bers, the said pistons having their axes in alinement with each other, the iston in the high pressure chamber constituting the hammer of the machine and the piston in the low pressure chamber being Ymoved in one direction in response to the exhaust motiveI Huid pressure, a spring for moving the lastnamed piston in theopposite direction, and

an 'operative connection between the 1ast' named piston 'and the drill steel, whereby.- as the piston is reciprocated, the drill steel is rotated, including a drill steel holder "formed with grooves, and parts carried bythe piston and engaging said grooves, subf 'stantially as described.

A '2. A rock drilling engine provided with high and lowpressure chambers, pistons in v'sad chambers, the piston in the high pressure chamber constituting the hammer and ooves 34 in the drill-steel holder, the spring chamber 27- the piston in the low pressure chamber being motive fluid actuated in one direction by the exhaust iiuid, a spring for moving the lastnamed .piston in the opposite direction, the last-named piston being composed of two collars having toothed engaging faces, one

collar being locked to a stationary .part of the engine against rotation, butlongitudinally movable, a drill steel holder having spiral grooves, and balls carried by the other collar and engaging the spiral grooves of the-drill steel'holder, whereby the latter is rotated as the piston in the low pressure chamber is reciprocated.v

3. A rock drilling engine provided with high and low pressure chambers, pistons in the respective chambers, the said pistons having their 'axes in alinement with each other, the piston' in the high pressure chainber constituting thehammer of the machine,

ing actuated in one direction by exhaust -motive fluid, a spring for actuating the lastnamed piston in the opposite direction, the

L the piston in the low pressure chamber be- 1 v.ico

the piston in the low pressure chamber be-V ing composed of vtwo 'collars having toothed engaging faces, one collar being locked to a stationary part of the engine against ro-v tation but longitudinally movable, balls carried by the other collar and engagingthe spiral grooves of the striking bar for drill steel rotating purposes, the piston in the low pressure chamber beingactuated in one direction by the exhaust motive fluid, a

spring for moving the last-named piston in the opposite direction.

5. rock drilling engine provided with high and low pressure chambers, pistons in' the respective chambers, the piston in the high pressure chamber constitutingthe hammer ofthe machine, the piston in the low pressure chamber lbeing composed of two collars having toothed engaging faces, one collar being'lockedto a Vstationary part of the engine against rotation but longitudinally movable. a lstriking bar carrying the drill steel and having spiral grooves, the

other collar havingf'balls engaging the spiral grooves of the striking bar for drill steel rotating purposes, -the piston in the low pressure chamberbeng actuated by the exhaust motive fluid, a spring for moving it in the opposite direction, and means for exhausting'the motive iiuid from the high pressure chamber through the low pressure chamber.

6. A rock drilling engine provided with high and low pressure chambers, pistons in the respective chambers, the piston in jthe high pressure chamber constituting the hammer of the machine and the piston in the low pressure chamber-.being composed of two collars having toothed engagmg faces,

Vone collar being locked against rotation but longitudinally movable, a striking bar carrying the drill steel and having spiral grooves, the other collar having parts engag- -mg the spiral grooves of the striking bar,

means for frictionally retarding the rotary action of' the striking bar in one direction to a greater extent than the frictional resistance offered by one of the toother col- 7. A rock drilling engine provided .with high and low pressure chambers, pistons in thel Vrespective chambers, the piston in the high-pressure chamber constituting the hammer of the machine, means for reciprocatingthe piston in the low pressure cham- -ber,' the last-named piston being composed of two collars having toothed engaging i faces, one collar being locked to a stationary part ofthe engine against rotation, but

longitudinally movable, -a striking bar carrying the drill steel, and having spiral grooves, the other collar having parts engaging the spiral grooves of the striking bar, and means for frictionally retarding the rotary action of the striking bar in one direction to a greater extent than the resistance offered to the rotary action of one of the toothed collars in the opposite direction.

-8. A rockdrilling engine provided with Vhigh and low pressure chambers, pistons in the respective chambers, the piston in the high pressure chamber constituting the hammer of the machine, means for reciprocating the piston in the low pressure chamber, the last-named piston being composed ofy two collars having toothed engaging faces, one col-lar being locked to a stationary part of the engine against rotationbut lonthe respective chambers in alinement'with each other, the piston in the low-pressure chamber forming a-ring through which exhaust from both chambers passes, the exhaust from the high-pressure chamber entering the low-pressure chamber and serving to move the piston therein in one direction, the high-pressure piston entering the ring of the low-pressure piston and cutting off the exhaust therethrough during the movement of the low-pressure piston.

10. A rock-drilling engine provided with high and low-pressure chambers, pistons in the respective chambers in alinement with each other, the piston in the low-pressure chamber forming aring through which eX- haust from both chambers passes, the exhaust from the high-pressure chamber entering the low-pressure chamber and serving to move the piston'therein in one direction, the high-pressure piston entering the ring of the low-pressure piston and closing the opening therethrough whereby the escape of the exhaust motive-fluid from the lowpressure chamber is prevented during the forward movement of the low-pressure plston, and means for reversing the movement of both pistons, the rearward, travel of the high-pressure piston being more rapid than that of the low-pressure piston.

' 11. A rock-drilling engine equipped with a rotatable drill-steel, the engine being provided with high and low-pressure chambers, pistons in the res ect'ive chambers in alinement with each ot er, the piston in the lowpressure chamber forming a ring through which exhaust from both chambers passes, the exhaust fromA the high-pressure chamber entering the low-pressure chamber and serving to move the piston in the last-named chamber in the forward direction, the highpressure piston entering the ring-opening of the low-pressure piston and fitting closely therein, whereby the escape of the exhaustmotive-Huid from the low-pressure chamber is cut. ofi' during the forward movement of the low-pressure piston, means for reversing the movement of the two pistons, the reverse-travel of the high-pressure piston being more rapid than that of the low-pressure piston, and an operative connection between the low-pressure piston and the drillsteel for imparting rotary movement to the latter.

12. A rock-drilling engine provided with high and low-pressure chambers, pistons in the respective chambers, the axes of the pistons being in alinement, a drill-steel holder, the piston in the lowpressure chamber forming a ring and the piston in the highpressure chamber constituting a hammer which strikes the drill-steel holder after entering the opening of the low-pressure piston, means for permitting the exhaust from Vthe high-pressure chamber to enter the low pressure chamber and act on the low-presmeans for imparting reverse movement to sure piston to move the latter forwardly, both pistons.` Y

means for allowing theexhaust-motive-fluid In testimony whereof I alix my signature to escape from the low-pressure chamber in presence of two witnesses.

after the low-pressure piston has made CHARLES T. CARNAHAN'. its forward stroke, an operative connection Witnesses: between the low-pressure piston and the F. E. BOWEN,

drill-steel holder for rotating the latter, and 4 HoRrENsE Umour 

